4wd is never meant to be used on hard dry pavement which is where you'll feel this binding sensation the most. All 4wd systems lock the front and rear driveshafts together so they must turn at the same speed. If you could look down on any vehicle when it is turning, you would see that the rear tires always travel through a smaller diameter circle so they travel a shorter distance. (Look at the four tire tracks in the snow). By nature of the front and rear pairs of tires being forced to turn at the same speed, the front tires are trying to rotate too fast and the rear tires are trying to turn too slow. Some of the tires have to slide. Since they try to stick to the pavement, the rubber sidewalls flex as much as possible until the tread is forced to slide. It can feel like the front of the truck is walking or bouncing.
This sliding puts a lot of pressure on the suspension and driveline components and causes rapid tire wear. On snow and ice, the tires can slide freely so you won't notice a problem. 4wd should never be used on the highway unless you're as crazy as I am and you try to go 65 mph in heavy snow. (I do that with an old fwd '88 Grand Caravan).
All wheel drive, (as opposed to 4wd) is not the same thing. AWD Caravans and Aerostars drive all four wheels all the time, but a fluid coupling is between the front and rear driveshafts so they are free to turn at different speeds. There's no switching these systems on or off, and you'll never feel them working. Those systems are specifically NOT called 4wd systems because manufactureres don't want owners to think they are suitable for off-road use.
Thursday, February 25th, 2010 AT 2:57 AM